Allow users to change the length of Bluetooth discoverability to

Allow users to change the length of Bluetooth discoverability to
be two minues, five minutes, an hour, or forever discoverable.

This addresses the internal bug 2413429:
	http://b/issue?id=2413429
and external issue 6348:
	http://code.google.com/p/android/issues/detail?id=6348

Original Author: Chris Wren <crwen@google.com>
Modifications done by: Jaikumar Ganesh<jaikumar@google.com>

Change-Id: Ie12e56ac41aa01a161d263c7525b6e021d4eeb1f